Air compressor motor help/Capacitor

[zchrisz]

Hello,

i have a central pneumatic 60 gallon 5hp air compressor with the Italy pump and a century 5hp ac motor.

the other day in the garage it kicked on normally and i heard a pop and there was electrolytic fluid and smoke pouring from the start capacitor.

i replaced the capacitor with the same value turned it on and within 5 seconds it popped that one. i did some research and found that the motors use a switch on the back to disconnect. i removed the back of the motor tested the switch which appears to be working via multi meter. the flyweight plunger on the shaft appears to be working i can push it in and it has some resistance but smooth.

any thing else i should look for? could the start windings have gone bad?

thanks!

 

[Max]

Hello,

i have a central pneumatic 60 gallon 5hp air compressor with the Italy pump and a century 5hp ac motor.

the other day in the garage it kicked on normally and i heard a pop and there was electrolytic fluid and smoke pouring from the start capacitor.

i replaced the capacitor with the same value turned it on and within 5 seconds it popped that one. i did some research and found that the motors use a switch on the back to disconnect. i removed the back of the motor tested the switch which appears to be working via multi meter. the flyweight plunger on the shaft appears to be working i can push it in and it has some resistance but smooth.

any thing else i should look for? could the start windings have gone bad?

thanks!

Was your replacement cap a start cap? And it was the same working voltage?

 

[zchrisz]

Was your replacement cap a start cap? And it was the same working voltage?

Yes to both.

 

[Max]

Ok it’s most likely not the cap then. I’d still suspect the switch, but I have to admit I am not a motor expert. I would suggest posting this in the electrical sub forum where it will get more attention from the right people.

 

[MovingAlong]

I'd be looking at the centrifugal switch. Jeremy Fielding has a good video on it..

Especially from your description of how the new cap blew up upon start...

 

[zchrisz]

great video. thanks for the link.

i put the old capacitor back in to fire the motor to watch the switch and it's working fine.

the capacitor still reads capacitance but it blew a hole in the end where the wires connect where the fluid leaked out. i'm wondering if the capacitor i replaced it with was faulty.

i'll have to try another one.

 

[dogdog]

Try to test the motor without the belt on first

 

[evildky]

did you replace or reinstall the bleed down capacitor? I recently did mine, start and run capacitors wiht new bleed down resistor, working like a champ.

 

[MovingAlong]

did you replace or reinstall the bleed down capacitor? I recently did mine, start and run capacitors wiht new bleed down resistor, working like a champ.

You're talking about this resistor? I'd not seen that before but haven't worked on every motor out there either. From that same link: "Most start capacitors do not have a resistor."

But yeah, if it was there on the original design can see where it would need to be there on the replacement. Learned something new this morning...

 

[fitter30]

Resistor is just for voltage bleed down. Take another look at the centrifical switch and its contacts spray it with some wd 40 or something like it.

 

[firebirdparts]

It should be possible to determine, when you run it next, that the start cap switch did shut off. I think that's the first thing you need to decide. if it didn't, then consider that the real problem was the motor isn't coming up to speed but the switch works correctly. I'm not saying that's the problem, I'm just saying consider that.

 

[evildky]

You're talking about this resistor? I'd not seen that before but haven't worked on every motor out there either. From that same link: "Most start capacitors do not have a resistor."

But yeah, if it was there on the original design can see where it would need to be there on the replacement. Learned something new this morning...

My compressor had one. When I was researching relacing mine it sounded like all had them and that it was pretty necessary to keep the capacitors alive. You can buy the resistors separately, they are cheap, might be worth a shot. Honestly its' all a bit over my head, I just fumbled my way through it.

 

[RPH]

If you have ever been zapped by a large capacitor. Then you appreciate bleed resistors. Even static can build up in a capacitor. That’s why some come shorted from the manufacturer.

 

[zchrisz]

Just an update.

originally the compressor kicked on and blew the start capacitor. i bought a cheap on off amazon same specs, blew that instantly when i turned it on.

i then took the motor apart and inspected the start switch. i cleaned the contact and tested the flyweight for operation.

i then put the old start capacitor that blew back in and started the motor real quick with the belt off while observing the flyweight switch and it operated as intended.

put everything back together ordered different capacitors off amazon and it's now working.

either the amazon replacement capacitor was bad or the start switch was stuck or something.

she's running now. thanks for the replies!